Hot-water generator

ABSTRACT

The hot-water generator has at least one whirling-muffle burner at the entry to the combustion gas flue so as to direct a combustion gas of high heat, e.g. 1,700* C., against contactheated heating surfaces in the flue. The heating surfaces are subdivided so that the first heating surface encountered by the gas flow carries only a part of the total water flow. Succeeding heating surfaces carry increased proportions of the total water flow.

I United States Patent A g Q I m13,608,527

[72] Inventor Werne Stl e'l 2,699,759 1/1955 Kuhner 122/421 Wintherthur, Switzerland 2,927,632 3/ 1960 Fraser 431/158 X [21] Appl. No. 875,675 3,228,451 1/1966 Fraser et a1. 122/23 X [22] Filed Nov. 12, 1969 2,994,308 8/ 1961 Stabenow 122/406 [45] Patented Sept. 28, 1971 3,162,179 12/1964 Strohrneyer, Jr. 122/448 X [73] Assignee Sulzer Brothers, Ltd. 2,923,348 2/1960 Fraser 431/158 Winterthur, swlilel'llnd FOREIGN PATENTS Pmmy 25: 73 465,280 5/1937 Great Britain 122/356 [31] 14977/69 Primary Examinerl(enneth W. Sprague Artomeys-PKenyQn Kenyon Reilly Carr & Chapin [54] HOT-WATER GENERATOR 7 Claims, 2 Drawing Figs.

[52] U.S.Cl 122/235 R,

' 431/158 ABSTRACT: The hot-water generator has at least one [51] ll!- hi |i g m burner at h entry to the combustion g flue FIG! 0 Search so as to di a combustion g f hig heat g IJOOO C. 42L 448; 8 against contact-heated heating surfaces in the flue. The heat- 56 R f d ing surfaces are subdivided so that the first heating surface en- 1 e erences l e countered by the gas flow carries only a part of the total water UNITED STATES PATENTS flow. Succeeding heating surfaces carry increased proportions 1,816,434 7/1931 Kaemmerling 431/173 X ofthe total water flow.

PATENTED SEP28 197i SHEET 1 [IF 2 Inventor- WERNER STIEFEL.

PATENTED SEP28 I971 SHEET 2 OF 2 Inventor: M/EQNER 57/2 F/EL (5/ f f W HOT-WATER GENERATOR This invention relates to a hot-water generator. More particularly, this invention relates to a hot-water generator having contact-heated heating surfaces.

Hot-water generators have been known in which fuel has been burned with a great excess of air in a relatively large space while the walls delimiting the space have been cooled. However, the cooled delimiting walls of the combustion chamber form radiant-heat surfaces in which the quantity of heat transmitted by flame radiation is greater than the quantity of heat transmitted through contact. Consequently, the floor area and space requirements of such hot water generators have been relatively great.

It has also been known to send the entire quantity of water supplied to a hot-water generator through the heating surfaces therein. However, since the outer wall temperature of the contact-heated surfaces must not fall below the condensation point of the combustion gas, for example, 140 C. as damage to the heating surfacesmay otherwise occur due to condensation-point corrosion which is especially deleterious where the burning fuel oil has a sulfur content, provision must be made to prevent such. Accordingly, ithas been known to mix the hot water emerging from the hot-water generator into the water flowing into the hot-water generator in order to raise the temperature of the supplied water and thus avoid condensation-point corrosion. This has, however, required a relatively large quantity of hot water to be mixed into the supply water and has therefore been unreasonable.

Accordingly, it is an object of the invention to eliminate the need of radiant-heat surfaces in hot-water generators.

It is another object of this invention to subject the contactheat surfaces of a hot-water generator to a relatively large heat loading.

lt is another object of the invention to provide a hot-water generator of compact construction.

It is another object of the invention to avoid condensationpoint corrosion on the heating surfaces of a hot-water generator.

It is another object of the invention to raise the temperature of water fed into a hot-water generator in an efficient manner.

Briefly, the invention provides a hot-water generator constructed with at least one whirling-muffle burner at the entry into a combustion gas channel i.e. a flue having contactheated heating surfaces therein. The combustion gas which is produced in the burner emerges with a temperature of at least 1700 C. and encounters the contact-heated surface in the flue. The area and volume occupied by the hot water generator is substantially reduced because of the use of whirling-muffle burners as the volume of these burners is substantially smaller than that of those previously used in the combustion chamber of hot-water generators. The whirling-muffle burners are operated so that an approximately stochiometric combustion, that is, combustion with a minimal air-excess of about 1.02 takes place. This combustion moreover occurs adiabatically, that is, with no intentional conducting away of heat at the walls of the muffle burners and is terminated at the outlet from the m uffles. The substantial diminution of space required is moreover made possible since the hot combustion gas emerging from the muffle burners is conveyed directly to the contact-heated heating surfaces. Heating surfaces heated through flame radiation are therefore avoided. By radiantheat surfaces are meant those surfaces with which the quantity of heat transmitted by flame radiation is greater than the quantity of heat transmitted through contact. Thus, by means of the invention it is possible to obtain, in a simple manner, a compact type of construction for hot-water generators.

In accordance with one form of the invention, the contact heated surface is subdivided into at least two sections which are disposed in sequence in the main stream of combustion gas. Also, only a part of the total quantity of water supplied to the hot-water generator flows through the first heating surface section encountered by the emerging combustion gas. For example, a maximum of 60 percent of the quantity of water supplied to the hot-water generator is directed to flow through the first heating surface section. By means of this further development, it is possible in a simple way to keep above the minimum outer wall temperature of the heating surface needed for the condensation point of the combustion gas and to prevent the maximum outer wall temperature from exceeding a limit value.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a horizontal section through a hot-water generator according to the invention; and

FIG. 2 graphically illustrates the water and gas temperatures along the water-impinged heating surfaces.

Referring to FIG. 1, the hot-water generator has a cooled combustion gas flue 4 of rectangular cross section which is delimited by tubes 3 welded together into a gas tight casing. The tubes 3 are connected to a collector l and a distributor 2 at opposite ends in order to receive and conduct flows of water therethrough. The collector 1 and distributor 2 each form a rectangular frame of quadratic periphery matching the rectangular cross section of the channel 4. The distributor 2 is directly connected to a combustion gas flue 7 which has an outlet leading into a chimney 8. A wall 5 is secured, as by welding into the frame formed by the collector 1 and a plurality of, for example, four, whirling burners 6 are mounted with muffles having their outlet in the wall 5. Fuel and air are supplied to the burners 6 by pipes 40, 41 respectively.

The burners 6 each consist of a muffle, lined with a ceramic material, and of a fuel-supplying device, surrounded by at least two coaxial annular channels for the combustion air, in which whirl-producing devices are installed. The fuel, gas and/or oil, which is supplied through the pipe 40 is thus burned in a stream of air that has a helical movement. In addition, the combustion is terminated at the outlet from the muffle and is effected with minimal excess-air. The rate of combustion is such that the combustion gas leaving the muffle has a temperature of at least 1700 C.

The generator further has a contact-heated heating surface in the flue 4 which is formed of two separated sections 10, 15 arranged consecutively in the flow of combustion gas (arrow 9). The heating-surface section 10, first encountered by the gas emerging from the burners 6, consists of a number of tubular coils arranged uniformly over the cross section of the combustion gas flue 4. The tubular coils start out from a distributor 11 and have their outlet into a collector 12 outside the flue 4 which is connected by a pipe 25 to a distributor 13 for the tubular coils of the second heating-surface section 15 in the stream of combustion gas. The tubular coils of the second section 15 are likewise distributed uniformly over the cross section of the combustion gas flue 4 with the last coils in the stream of gas being provided with fins 16. In addition, metal sheets 17 are provided between the bends of these coils and the adjacent wall of the flue 4 for throttling the stream of gas. The tubular coils of section 15 have their outlets connected into a collector 14 outside the flue 4 which is connected by a pipe 26 with the distributor 2 of the combustion gas flue-wall tubes 3.

In order to supply water to the hot-water generator, a pipe 23 having a water-circulating pump 21 therein forks downstream of the pump 21 into a first branch pipe 27 and a second branch pipe 28. The first branch pipe 27 is connected, by way of a valve 22, with the distributor 11 of the first heating-surface section 10 while the second branch pipe 28 connects to a pipe 29 which connects, by way of a valve 24, to the connection pipe 25 between the collector l2 and the distributor 13. In addition, the branch pipe 28 has an outlet, by way of a valve 30, into the connection pipe 26 between the collector 14 and the distributor 2.

In order to remove water from the hot-water generator, the collector l is connected to a pipe 32 which conducts the hot water produces to the consumers, which water, after giving off heat arrives, through the intermediary of a network (not shown) by way of a pipe 20, into the supply pipe 23. Additionally, a mixing pipe 33 is connected between the pipe 32 and the pipe 20 and includes a valve 34 therein so that a quantity of produced hot water can be mixed with the cooled water (eg at 60 C.) flowing back through the pipe 20.

During operation of the generator, the valve 34 in the mixing pipe 33 is opened to a degree so that the water flowing in the pipe 32 into the hot-water generator has a temperature of about 85 C. The other valves 22, 24, 30 are also regulated so that a portion of the total flow, not to exceed 60 percent, for example, 45 percent enters through the completely opened valve 22 into the first heating-surface section 10. Another 45 percent of the quantity of water flowing into the hot-water generator arrives, by way of the pipes 28 and 29 and the valve 24, set into a throttling position, into the connecting pipe 25, where the water mixes with the water emerging from the first heating surface section 10. The mixed water then arrives, by way of the distributor 13, into the tubular coils of the second heating-surface section 15. The remaining percent of the quantity of water supplied through the pipe 23 to the hot water generator flows by way of the pipe 28 and the valve 30, into the connecting pipe 26, where this water becomes mixed with the water coming out of the second heating-surface l5. Thereafte, the entire 100 percent quantity of water flows by way of the distributor 2 through the wall pipes 3, and leaves the hot-water generator through the pipe 32.

The temperature of the combustion gas and of the water reached during this operation are shown approximately in FIG. 2. For example, the combustion gas produced in the burners 6 emerges, at approximately l,800 C., into the combustion gas channel flue 4, where the staggered tubular coils of the first heating-surface section 10 are immediately encountered. Because of the very high heat load, a temperature above the condensation point exists on the outside of these coils, of for example 140 C. With the rapidly decreasing heat load, and because of the lessened quantity of water in section 10, the temperature of the water in the coils rises further above the condensation point, so that the outside temperature of these coils does not fall below the condensation point. The water leaves the first heating-surface section 10 with a temperature of about 150 C., at which temperature no evaporation occurs (point A). The mixing-in of 45 percent of the water at 85 C. then takes place in the distributor 13 with a mixture temperature of 1 17.5 C. (point B) resulting. Although the heat load in the second heating-surface section 15 is considerably lower than that in the first heating-surface section 10, because of the high mixture temperature and of the suitably selected flow speed, the outside temperature of the coils of the second heating-surface section 15 does not fall below the condensation point. The water then enters with a temperature of about 150 C. (point C) into the collector l4 and in the connecting pipe 26, because of the mixing in of the remaining 10 percent of the water at about 85 C., reaches an approximate temperature of l43.5 C. (point D). During the following flow through the wall tubes 3, the water, in counterflow to the combustion gas, becomes heated once more to 150 C., at which temperature the water leaves the hot-water generator through the pipe 32.

in accordance with one way of carrying out the invention a regulating means can be used to proportion the water between the sections l0, 15. For example, a temperature-sensor 50, may be provided at the collector 12 which, through the intermediary of a regulator 51, closes the valve 24 in the pipe 29 in such a way in response to the sensed temperature that more water than previously flows into the first heating surface 10 when the temperature of the water in the collector l2 rises. in an analogous way, a similar regulatory arrangement 50, 51 may also be provided, between the collector 14 and the valve In accordance with a further form of construction of the invention, it is also possible to provide only one burner 6 in the wall 5. It is furthermore possible to provide, instead of the two heating-surface sections 10, 15 three such sections in the combustion gas flue 4 with a proportioning of the water flow therein to achieve the proper temperatures above the condensation point.

What is claimed is: l. A hot-water generator comprising a flue, a contact-heated heating surface disposed in said flue for a flow of water therethrough, and at least one whirling-muffle burner disposed at the entry of said flue adjacent said heating surface for directing a flow of combustion of gas into said flue directly from said burner at a temperature of at least l,700 C. to encounter said heating surface. 2. A hot-water generator as set forth in claim 1 wherein said heating surface is divided into at least two sections disposed consecutively in said flue with respect to the flow of combustion gas and which further comprises means for delivering a part of the total quantity of water supplied to the generator to the first of said sections.

3. A hot-water generator as set forth in claim 2 wherein said means delivers up to 60 percent of the total quantity of supplied water to said first section.

4. A hot-water generator as set forth in claim 2 which further comprises means for delivering said part of the supplied water from said first section to the other of said sections at a mixing point and means for delivering a part of the remainder of the supplied water into said other section at said mixing point.

5. A hot-water generator as set forth in claim 4 which further includes regulating means for proportioning the water to said sections in response to the temperature of the water emerging from said first section.

6. A hot-water generator as set forth in claim 1 wherein said channel has a wall delimiting said channel and connected to said heating surface to define a second heating surface for the flow of the water therethrough in counterflow to the flow of gas in said channel.

7. A method of generating hot water in a generator having a flue and a contact-heated heating surface therein for a flow of water therethrough, said method comprising the steps of directing a combustion gas flow at a temperature of at least 1,700 C. into said flue to flow immediately across said heating surface therein, and

maintaining the temperature of the water in said heating surface above the condensation point of the combustion gas in said flow.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, .1 5 7 Dated September 28, 1971 HOT WATER GENERATOR Inventor-(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 7 4, change "produces" to --produced-- Column 3, line 2, change "Thereafte, to --Thereafter- Column r, line IT, "channel" should be --flue-- Column I, line 50, (Both occurrences) change "channel" to--flue-- Signed and scaled this 18th day of April 1972.

( SEAL Attest:

EDWARD I-I.I*"LETCII5JR, JR. ROBERT GOTTSCHALII Attesting Officer Commissioner of Patents ORM PC2-1050 (10-69) uscoMM-Dc 60376-F'69 9 U S GOVEHNMENT PRINTING GFFICE 196i 0-356-33l 

1. A hot-water generator comprising a flue, a contact-heated heating surface disposed in said flue for a flow of water therethrough, and at least one whirling muffle burner disposed at the entry of said flue adjacent said heating surface for directing a flow of combustion of gas into said flue directly from said burner at a temperature of at least 1,700* C. to encounter said heating surface.
 2. A hot-water generator as set forth in claim 1 wherein said heating surface is divided into at least two sections disposed consecutively in said flue with respect to the flow of combustion gas and which further comprises means for delivering a part of the total quantity of water supplied to the generator to the first of said sections.
 3. A hot-water generator as set forth in claim 2 wherein said means delivers up to 60 percent of the total quantity of supplied water to said first section.
 4. A hot-water generator as set forth in claim 2 which further comprises means for delivering said part of the supplied water from said first section to the other of said sections at a mixing point and means for delivering a part of the remainder of the supplied water into said other section at said mixing point.
 5. A hot-water generator as set forth in claim 4 which further includes regulating means for proportioning the water to said sections in response to the temperature of the water emerging from said first section.
 6. A hot-water generator as set forth in claim 1 wherein said channel has a wall delimiting said channel and connected to said heating surface to define a second heating surface for the flow of the water therethrough in counterflOw to the flow of gas in said channel.
 7. A method of generating hot water in a generator having a flue and a contact-heated heating surface therein for a flow of water therethrough, said method comprising the steps of directing a combustion gas flow at a temperature of at least 1, 700* C. into said flue to flow immediately across said heating surface therein, and maintaining the temperature of the water in said heating surface above the condensation point of the combustion gas in said flow. 